The U.S. Secret Service will not be able to pay an estimated 1,100 employees for required overtime work after September due to government-imposed pay caps, the agency's chief said on Monday.

In a statement, Secret Service Director Randolph “Tex” Alles attributed the funding shortfall to the cost of protecting President Donald Trump and his family, and “an overall increase in operational tempo.”

The Secret Service did not immediately respond to a request for comment.

In an interview with USA Today, which first reported the story, Alles noted that the Secret Service's mission was set by law and that he did not have authority to curtail it.

“The president has a large family, and our responsibility is required in law,” Alles told the newspaper. “I can't change that. I have no flexibility.”

The agency must protect a record 42 people, including 18 Trump family members, up from a total of 31 during the administration of former President Barack Obama, he told USA Today.

The problem did not start with the current president's tenure, “but rather has been an ongoing issue for nearly a decade,” Alles said in the statement.

U.S. Secret Service agents arrive on a backup helicopter following President Donald Trump at Joint Base Andrews outside Washington, before Trump travels to Bedminister, New Jersey, June 9, 2017.

Alles has asked lawmakers to raise the combined salary and overtime cap for agents from $160,000 a year to $187,000 for at least the period of Trump's first term, USA Today reported.

But even if such a proposal was approved, about 130 veteran agents would not be fully compensated for hundreds of hours already amassed, the newspaper said, citing the agency.

The White House said in a statement that the Trump administration would work with Congress on the issue.

“The president is committed to ensuring the Secret Service and all of those protecting our country have all the resources they need,” it said.